About BestForecast

What is BestForecast?BestForecast is Weather Underground’s proprietary forecasting system that uses multiple weather forecasting models, combined with our predictive algorithm, to create the most accurate forecast.

Evolution/VerificationWe started verifying our old forecasting system back in 2005, which was directly from the Global Forecast System (GFS) and model output statistics (MOS) designed by Dr. Masters. We looked at two variables--highs and lows--for every airport around the globe, since airport weather stations are considered the most accurate. By evaluating our forecasts and the predictions from the GFS, we were able to create an algorithm that better predicted daily highs and lows. This was the first generation of BestForecast.

From there, we implemented several numerical models such as MOS, GFS, ECMWF, GEM, NAM, SREF and NAFES into our verification and forecast system. You can find more information about all these models from NOAA. Other important weather variables such as hourly temperature, wind, pressure, cloud cover, and humidity were added into our system. Then, we took it further by producing a forecast for each hour of the day, which enables us to bring you more accurate and detailed forecasts.

Weather Underground now integrates about 140+ possible forecasts with 8 to 10 weather variables into our system. We now deliver forecasts for temperature, dew point, humidity, pressure, wind, weather conditions, probability of precipitation, and cloud cover out to 10 days.

Personal Weather Station(PWS)Weather Underground has the largest network of weather observations in the world. In addition to more than 34,000 stations which are owned and operated by government organizations, we have a network of 24,000 personal weather stations across the globe.

Location is an important consideration in BestForecast. Was this forecast made for my neighborhood or the nearby airport, which could be up to 60 miles (100 km) away? Most weather sites can only estimate your neighborhood weather conditions and provide you the closest airport weather observations and forecast . However, Weather Underground gives you options to select any neighborhood you’d like, not just the closet airport, and the forecast is tailored-made to each individual station. Adding personal weather stations into the system brought BestForecast into another generation.

As per our founder and Director of Meteorology, Dr. Jeff Masters: “We gather several years of weather data from a site and optimize the forecast to suit the unique microclimate of a particular station. Thus, "backyard meteorologists" that own and maintain one of the more than 24,000 personal weather stations that record and send live weather conditions to Weather Underground will now have a forecast specifically generated for their own backyard. BestForecast also gives the expected precipitation amounts (in inches), and provides ten days of forecast information, instead of the seven days provided by the National Weather Service.”

As our PWS network continues to grow, we not only need to constantly maintain our computer workload but also optimize its performance. We’d like to deliver the most updated forecast as often as possible and as soon as it becomes available.

With the recent spate of snow storms in the northeast US, I've been finding BestForecast hourly forecasts to be significantly off in terms of precipitation prediction, timing and actual conditions on the ground. Even this morning, a quick comparison of NWS and BestForecast for snow in CT show major differences with NWS predicting accurately and BestForecast predicting less precipitation and arrival hours later. My friend timed their departure from Mass. to drive south based on BestForecast did not appreciate the errors…

Last week BestForecast was way off in terms of precipitation timing and total accumulation in southern CT….

I have contributed to WU with aprox 8 pws in Central America and more particular in Guatemala, I really rely on WU forecast, and I agree and feel that BestForescast is Indeed best.

Still have some issues, but for example, in the area I cover (Central America) with particular weather conditions not found anywhere else, having 2 different oceans so close, we have a lot of weather makers. This combined with terrain and elevation makes another issue in weather. Not the mention the scarse coverage of stations and due to connection constraints, not all live if available.

WU's BestForecast is better than the normal NOAA / GFS, but I guess could be better if you take in account altitude. We have cities for example IQUETZAL1 (MGQZ) with below 0°c temps in the morning and 20 miles south MGRT with above 20°c lows the same day, WU Bestforecast can deal with this, but still some missed I guess due to altitude corrections or not taking much in account our local PWS.

Based on my observations, in general I can say BestForecast is better in terms of temperature prediction than in precipitation, temperature fcst could be enhanced taking in account altitude (and smaller grid maybe), but PCPN is a big deal in rainy season down here.

Quoting EvPv:I do not know what area my town (Liberty, Maine) is linked into but the BestForecast is way off. The forecast temps for THAT day and the following days is 5-15° warmer than NWS and what actually occurs....

I am going to have to agree with EvPv. The temperatures for zip 72210 are wildly too high (up to 15° higher) compared to both the NWS and your own BestForecast for a zip code less than six miles away. If you compare 72210 (west Little Rock, AR) with 72201 (downtown Little Rock) -- the numbers are extremely different.

Can I call you Wonder?I have been running my station here in Mexico for 6 years and I am pleased to part of the organization.Getting this newsletter from Dr. Jeff is certainly a step in the right direction as I feel we have largely been ignored in the past. My complaint is the difficulty in communication with the staff. Some time ago I was concerned about the program recording the number of hits our stations were getting. It would zero half way through the month. It did eventually get fixed but your people didn't think it a big deal. Let me tell you it is a big deal with us, we really want to know who is checking in on us.

Next, I would really like a small space to pass info on to our readers. To let them know if we have a problem with something or other. To keep them informed and make them feel part of the organization. Is this possible? If I am down for any reason I get e-mail asking me what is happening with the station. In the hurricane season this is most important.

Also a couple of years ago I wanted live 24/7 video link to show sailors and surfers local wave conditions. Your one frame a minute would not cut it. Eventually I adapted a digital camera to serve the purpose. It became very popular and still is. But it is hard to maintain and secure. Are there any plans to make a video connection, in the works?

Quoting EvPv:I do not know what area my town (Liberty, Maine) is linked into but the BestForecast is way off. The forecast temps for THAT day and the following days is 5-15° warmer than NWS and what actually occurs. I use W.U. for the radar and to check the PWS that is located about a half mile from my house (when I'm at work). I bike everyday of the year (sold my car in 2008), so the forecast temps are crucial for me in planning long adventures on my days off. Since BestForecast was introduced I have never gone to NWS as much as I do now.

This is a great idea. I see temp variations all the time in Maine, however I'm wondering how long until it shows any value to me.

I have a PWS and have kept daily readings since 1/1/98. I've given thought to feeding into the W.U. system, even with the station logging in a half mile away. However, the current setup on W.U. has really diminished its value to me.

Hi EvPv - just wanted to check: you have seen the switch that enables you to toggle between our forecasts and the NWS - at the top of our city forecast pages...?

http://www.wunderground.com/q/zmw:04949.1.99999 - I'm not sure which station you're looking at but our high temperatures have been more accurate than the NWS for the default station in Liberty, Maine - have you been looking at the verification at the bottom of the forecast module? Perhaps you're using a different station - please let us know and we will look into it for you. Thanks!

Quoting ibikeride2:The NWS provides a more accurate forecast compared to Best Forecast. I found Best Forecast to be inaccurate in temperatures forecasts and wells as the actual forecast descriptions.

You can track the temperature accuracy of both BestForecast and NWS at the bottom of each Forecast module on our city forecast pages.... and just to check, you've seen the switch to change between forecast types, right!?

Please can you let me know your ZIP so we can check into our forecasts - Thanks very much

This is awful. The forecasts are often incorrect, particularly the sky conditions which are annoyingly listed first. The syntax is machine-like and quirky. I have gone to the local NWS office webpage for forecasts, which is a pain. Revert or give me the option.

I would like to add that Proper calibration of the PWS's sensors is a must if we are to move forward with making Best Forecast have zero errors. Once a year I have the sensors of my station calibrated and verified. I have seen allot of PWS with readings the seem like they are way O.O.T. Out Of Tolerance. Please conceder keeping your station adjusted and calibrated to its specifications, Sensors and instruments drift over time.

I do not know what area my town (Liberty, Maine) is linked into but the BestForecast is way off. The forecast temps for THAT day and the following days is 5-15° warmer than NWS and what actually occurs. I use W.U. for the radar and to check the PWS that is located about a half mile from my house (when I'm at work). I bike everyday of the year (sold my car in 2008), so the forecast temps are crucial for me in planning long adventures on my days off. Since BestForecast was introduced I have never gone to NWS as much as I do now.

This is a great idea. I see temp variations all the time in Maine, however I'm wondering how long until it shows any value to me.

I have a PWS and have kept daily readings since 1/1/98. I've given thought to feeding into the W.U. system, even with the station logging in a half mile away. However, the current setup on W.U. has really diminished its value to me.